In a typical TIG welding process, the electrode is not touched to the workpiece to initiate the welding arc. Instead, the electrode is maintained at a space from the workpiece to establish an arc gap. The arc is initiated through an arc starting apparatus, which is usually a high frequency, high voltage generator that creates an high frequency voltage burst of energy across the gap to start the arc. A high frequency generator to create the high frequency, high voltage burst across the arc through the power lead from the torch to the power source is the arc starter to which the invention is directed. Manufacturers of TIG welders have been challenged to produce a solid and good arc start every time, especially when the tungsten electrode is cold or contaminated. Conventional wisdom has been to increase the arc starter intensity by increasing the spark gap distance of the high frequency spark gap generator. The increased intensity assured that the arc jumped the gap between the electrode and workpiece. However higher intensity for the starting pulse or burst created more electrical noise radiated from the power lead acting as a transmitting antenna. This problem was amplified during AC TIG welding where the high frequency burst is required during each polarity reversal. Rapid succession of high intensity starting bursts caused substantial EMF interference. Radiated electrical noise has been the source of component failure and interference with surrounding electrical equipment adjacent the TIG welder. Thus, there is a need for a torch used in TIG welding, which torch can create a positive arc upon receipt of a lower intensity high frequency burst which need not be increased so there is extensive noise radiated to the surrounding environment. Thus, there is a need for a TIG torch that improves the arc starting ability while reducing the radiant electrical noise associated with conventional TIG welders by a reduced intensity and by allowing shielding of the power lead that radiates the noise.
As further background, a conventional TIG welding torch includes a flexible tube extending from the power source to the torch and including a gas or water passageway and a power lead so that the power lead directs welding current from the power source to the electrode in the torch. The tungsten electrode is electrically connected to the power source through the power lead inside the flexible tube or cable that is connected to a conductive collet that holds the tungsten electrode. Surrounding the tungsten electrode and conductive collet there is a component referred to as a gas nozzle that is formed from a non-conductive material, such as ceramic. This gas nozzle is mounted in a non-conductive body having a back cap that is manually manipulated during the TIG welding process. The present invention is also useful for starting the plasma arc of a plasma cutter wherein the torch is connected to the power source by a flexible tube including a power lead and a gas passageway. The power lead is connected to the fixed electrode within the plasma cutter torch, which electrode is surrounded by a nozzle similar to a conventional TIG welding torch. The high frequency, high voltage burst on the power lead used in a plasma arc cutting torch creates an arc between electrode and nozzle, which arc is then transferred by standard voltage increases associated with a plasma cutting process. Both the conventional TIG welding torch and a plasma arc cutting torch requires a burst of high frequency, high voltage energy for starting the arc. There is a need to decrease the intensity of this high voltage, high frequency energy burst while assuring that the level of energy positively starts the arc. The present invention accomplishes this objective by modifying a conventional TIG welding torch and is secondarily applicable to an improvement in a plasma arc cutting torch.